1. Field of the Invention
The present invention relates to automated manual transmissions, particularly automated manual transmissions employing constant mesh gears using sliding jaw clutches to selectively engage a desired gear ratio, used in combination with turbocharged internal combustion engines. In particular, the present invention relates to control of the operating parameters of the engine to which the transmission is coupled and control of the transmission and coordinating control of the two.
2. Description of the Prior Art
Known automated manual transmission shift control strategies are based on commands of a transmission electronic control unit to an engine electronic control unit for particular speeds and loads during gear changes. The automated manual transmissions employ sliding jaw clutches and are typically not suited for power shifting. To achieve a shift, engine power typically must first be reduced. There is typically an associated decrease in the engine""s turbocharger boost pressure during the shift event, resulting in less than optimal vehicle performance.
Known automated manual transmission equipped vehicles, typically trucks, rely on a throttle or fuel rack or foot pedal position sensor providing a corresponding signal, an engine speed sensor, and a vehicle speed sensor to determine driver demand and corresponding engine and transmission operating conditions. Under heavy acceleration conditions, the driver pushes the foot pedal to floor. Displacement of the foot pedal to the floor yields approximately 100% of the available foot pedal position sensor travel. The engine responds by increasing the rate at which fuel is metered to the engine (the fuel rate) until maximum power is achieved. At this point, the next transmission gear is selected to enable the continued acceleration of the vehicle. An industry standard controls communication protocol, such as SAE J1939, is employed to communicate commands within the driveline or powertrain system. The transmission overrides the signal from the foot pedal position sensor and commands the engine to go to a reduced speed and load while the transmission shifts out of gear. When the engine speed and load are decreased, the rotational speed of the turbocharger and the associated boost also decrease. Once the transmission has been shifted into the target gear, a command to restore full power is given. However, the engine""s response time is delayed at least in part by the time needed to spool up, or increase the rotational speed of the turbocharger. The described delay is commonly referred to as turbo lag. As subsequent up-shifts are made, the cumulative effect on the vehicle speed continues to increase as illustrated in FIG. 3. It is desired to have a method of controlling a powertrain system which minimizes the turbo lag associated with shifting of an automated manual transmission.
The present invention discloses a method for controlling up-shifting of a vehicular powertrain system used with a turbocharged internal combustion engine operating in a maximum foot pedal position travel or full load condition. The powertrain system includes a multiple speed change gear transmission and a control unit for controlling the engine and the transmission. The method includes the following steps. One or more engine operating parameters are selected for control by the control unit. The engine operating parameters include fuel injection timing, fuel injection rate, fuel injection pressure, turbocharger wastegate control valve setting, intake air throttle setting, variable geometry turbocharger vane position setting, engine valve timing setting and engine valve activation state. The control unit establishes that an up-shift is about to occur from a first gear to a second gear. Upon establishing that an up-shift is about to occur, the engine is placed in a transient operating mode. The transient operating mode includes the steps of: reducing a magnitude of at least one of the engine speed and the engine torque to enable shifting from the first gear, and simultaneously modulating the selected engine operating parameter to maintain a boost pressure (i.e., an elevated intake air or boost pressure produced by the turbocharger). The control unit establishes that the shift from the first gear has been completed. Upon establishing that the shift from first gear has been completed, the engine is returned to the full load condition. The selected engine parameter is immediately modulated so as to increase the torque output of the engine after the shift from the first gear. The modulation of the selected engine parameter is coordinated with the shifting of the transmission to decrease the turbocharger lag associated with shifting and to thereby decrease of a power output response time of the engine. Alternately, this shift control method can be used to reduce exhaust emissions during shift events.
Also disclosed is a control system for controlling up-shifting of a vehicular powertrain system used with a turbocharged internal combustion engine operating in a maximum foot pedal position. The powertrain system includes a multiple speed change gear transmission and a control unit for controlling both the engine and the transmission. The control unit has logic rules effective for implementing the following steps. The logic rules enable establishing that an up-shift is about to occur from a first gear to a second gear. Upon establishing that an up-shift is about to occur, the engine is placed in a transient shift operating mode. The transient shift operating mode includes the steps of: reducing a magnitude of at least one of the engine speed and the engine torque to enable shifting from the first gear, and modulating a selected engine operating parameter to maintain boost pressure (produced by the turbocharger) while the magnitude of the at least one of the engine speed and the engine torque is reduced. The selected engine operating parameter is chosen from a plurality of parameters including: fuel injection timing, fuel injection rate, fuel injection pressure, turbocharger wastegate control valve setting, intake air throttle setting, variable geometry turbocharger vane position setting and engine valve activation state. The logic rules further enable establishing that the shift from the first gear has been completed. The selected engine operating parameter is immediately modulated so as to increase the torque output of the engine after the shift from the first gear. The modulation of the selected engine parameter is coordinated with the shifting of the transmission to decrease the turbocharger lag associated with shifting, to thereby increase a power output of the engine substantially immediately upon completion of the up-shift.
The present invention provides a method of controlling a powertrain system, which minimizes the one of the turbo lag and the exhaust emissions which are associated with shifting of an automated manual transmission.